BEHAVIOR AND PERFORMANCE OF A DIAPHRAGM WALL FOR AN UNDERGROUND AUTOMATIC CAR PARK IN BANGKOK

Abstract

Currently, the use of underground automatic car parks is becoming increasingly popular in Bangkok as it can help maximize space usage without ramps. However, an automatic system requires large openings in the basement slab, resulting in the slab possibly having insufficient axial capacity. This paper focused on one of the latest underground automatic car park construction projects in Bangkok's city center, True Digital Park, which comprises a total of four basements with a 13.20 m maximum excavation depth, including mat foundation and lean concrete. An 800mm-thick diaphragm wall (D-wall) was proposed to serve as a soil-retaining structure with 3 layers of full-temporary bracing. The Finite Element Method (FEM) with the Mohr-Coulomb soil model was employed for the D-wall design and horizontal movement prediction, and the actual construction of the basement and building have since been completed. The field performance of the D-wall construction was evaluated through horizontal movement using installed inclinometers. During every stage of construction, including soil excavation and bracing installation, horizontal displacement was monitored carefully and strictly controlled to minimize the D-wall movement. The monitoring results showed suitable agreement with the FEM analysis. However, movement of the retaining wall was detected during upward construction, even though the basement was fully cast, suggesting insufficient axial basement slab capacity as well as care and control for similar projects. This article describes the construction and monitoring of the project together with field performance results.